18-8 type austenitic stainless steel, such as 1Cr18Ni9, 1Cr18Ni9Ti and 0Cr18Ni9 belongs to conventional austenitic stainless steel. It has found a extensive and long-term application in the industry because of its superior corrosion resistance, combined mechanical properties and processing property. However, because it contains a large amount of expensive Cr and Ni, the price of the steel is very high, thereby limiting its application in a broader field. Furthermore, because both Cr and Ni are scarce in the earth, it is a long-term goal of metallurgical field to develop an austenitic stainless steel containing little or no Cr, Ni so as to substitute for 18-8 type Cr-Ni austenitic stainless steel. Up to now, however, it has not been reported that a stainless steel without Cr and Ni can provide corrosion resistance, combined mechanical properties and processing property equivalent to that by conventional 18-8 type Cr-Ni austenitic stainless steel.
It is a main object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel.
It is another object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which can improve corrosion resistance, especially in sulfinic acid or a reductive medium.
It is again another object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which is in particularly resistant to intergranular-corrosion.
It is a further object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which has an improved toughness at a low temperature, especially at the temperature of -120.degree. C.
It is a further object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which has an improved corrosion resistance in hydrochoric acid, diluted sulfuric acid, basic solution and seawater.
It is a further object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which has an improved resistances to oxidation, heat fatigue and hot corrosion.
It is a further object of the invention to provide an Al--Mn--Si--N austenitic stainless acid-resisting steel which has an improved resistances to wear and high temperature.